Mechanism for inductive heating of surfaces



March 30, 1954 c. c. scHRG MECHANISM FOR INDUCTIVE HEATING OF' SURFACES Filed Dec. l5. 1949 Fig.1

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Patented Mar. 30, 1954 OFFICE MECHANISM FOR INDUCTIVE HEATING F SURFACES Carl Christian Schrg, Frankfurt am Main Hochst, Germany Application December 15, 1949, Serial No. 133,207

Claims priority, application Germany December 20, 1948Y 1 Claim. (Cl. 219-1051) In applied chemistry hot surfaces are often coated with liquids in a thin layer to evaporate all components simultaneously for avoiding fractionizing. Frequently gas is added to the vapour during the evaporating process for the purpose of a chemical reaction. A uniform temperature of the hot evaporated surface that musi; be observed exactly is required to avoid encrusting or explosive danger. With surfaces heated by fire there is the already known danger of local overheating and on account of considerable inertia of heat of the whole system there is only a limited exactness of control. With steam heating steam of high temperature requires high pressures, thereupon thick Walls and consequently an inertia of heat rendering diicult control.

According to the present invention those surfaces can be heated electrically by being developed as a short circuited secondary circuit of a transformer, in which the secondary circuit consists of one portion of low resistance and one portion of a higher resistance. The primary windings must be insulated heat resistant. The magnetic circuit is iron closed. The portion of the low resistance of the secondary circuit may also be laminated, should the opportunity arise, for avoiding losses, rising from displacement of current. With polyphase arrangement short circuit currents are running also between the diilerent phases that the plate is heated uniformly.

The invention is clearly illustrated in the accompanying drawings, in which:

Fig. 1 shows schematically and in cross section one form of the improved arrangement, and

Fig. 2 shows a similar View of a modified form thereof.

Referring now to the accompanying drawings, particularly Fig. 1, the secondary circuit comprises the parts 4 of low resistance (good electrical conductivity) which are connected in good thermal conducting relationship with the part I of relatively lower electrical conductivity. in the parts 4 the heat resistant and insulated primary windings 3 and the laminated magnetic legs 2 are connected with one another by yokes not shown.

In Fig. 2, an arrangement is shown which is particularly adapted for use in connection with chemical reactions in which evaporation must occur in a gaseous atmosphere. Here, the U- shaped part of the secondary circuit may be used for preheating the gas. The U-shaped part of the secondary winding again contains the heat resistant insulated primary winding 3 and the laminated core 2. This U-shaped part consists of concentric walls 4 and 5 deiining an interspace 6 through which the gas to be heated passes from inlet port 8 to exit ports l. Obviously, the inter-space may be composed of a number of parallel branches.

The arrangement has the special advantage of a uniform and easily regulatable temperature of the evaporating surface, since the thermal inertia is Very low. It may also be used for heating the bottoms of vessels, and if the bottom surfaces thereof are vaulted, matters may be arranged .so that, for example, three fourths of the secondary heating surface may project into the interior of the vessel, whereby the heat transmitting surface is greatly increased.

I claim:

An electric induction heating apparatus comprising a closed laminated iron magnetic circuit, a primary coil wound about a part of said iron circuit, and a short-circuited secondary circuit disposed in linx-linking relationship to said iron circuit, said secondary circuit consisting of two series-connected portions of which a first portion is made of a material of good electrical conductivity and formed as a double-wall shell of U-shape cross-section, and the second portion is formed as a plate of material of relatively lower electrical conductivity in good thermal transmitting relationship to the legs of said first portion, whereby a major portion of the heat developed in said secondary circuit will be developed in said second portion, and means defining uid entrance and exit ports communicating .with the interspace of said shell.

CARL CHRISTIAN SCHRG.

References Cited in the file of this patent UNITED lSTATES PATENTS 

